kotlinlang #codereview

Apparently such library doesn't exist. Even If it do, you still have to declare mapping rules. And if it so, what is the difference between declaring rules and instantiating an entity manually?

dstarcev

08/16/2016, 10:57 PM

Mapping rules shouldn’t be required in most cases, usually configuration is convention-based.

dstarcev

08/16/2016, 10:59 PM

I’ve found a library, will see if it’s good enough http://modelmapper.org/getting-started/

christophsturm

08/17/2016, 11:07 AM

@christophsturm has left the channel

bamdmux

08/24/2016, 8:42 AM

Im trying to make an extension function to split a collection of items in pairs and came with this

bamdmux

08/24/2016, 8:43 AM

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fun <T> Collection<T>.splitPairs(): List<Pair<T, T>> = withIndex()
        .partition { it.index % 2 == 0 }
        .let { it.first.zip(it.second) { a, b -> a.value to b.value } }

bamdmux

08/24/2016, 8:43 AM

but I don't know if theres a better solution than using zip

cleiter

08/24/2016, 9:17 AM

if you have lists you could use something like

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fun <T> List<T>.splitPairs2(): List<Pair<T, T>> =
    mapIndexedNotNull { i, item ->
        if (i % 2 == 0 && i < lastIndex) item to this[i + 1] else null
    }

but i think your solution is fine for collections

👍 1

bamdmux

08/24/2016, 10:07 AM

I guess I could transform the col to a list

deepanshu

08/28/2016, 11:35 AM

I’m writing the toString() method for an object and came up with:

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val value = StringBuilder("Variable1: $var1\n" +
                    "Variable2: $var2\n" +
                    "size: ${myList.size}\n")
for (item in myList) {
	val name = item.name
	val type = item.type
	val value = item.var1 - item.var2
	value.append("\t$name : $type $value\n")
}
return value.toString()

When I decompile the

.class

file this created, I see that there are too many StringBuilders being created. Any idiomatic way to avoid that?

vmironov

08/28/2016, 11:40 AM

You should avoid using string interpolation and

StringBuilder

at the same time, e.g.

value.append("\t$name : $type $value\n”)

may be replaced with:

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value.append("\t")
value.append(name)
value.append(" : ")
value.append(type)
value.append(" ")
value.append(value)
value.append("\n”)

The code is a bit less readable, but it prevents the compiler from creating useless

StringBuilder

objects

👍 2

deepanshu

08/28/2016, 11:53 AM

Yep, that’s exactly the issue. In addition to the

StringBuilder

objects created in the loop, it also creates one

StringBuilder

, each for the line

VariableN: $varN\n

. Seems that concatenation and interpolation also don’t play nicely

danielgomezrico

09/01/2016, 3:18 AM

Guys, Im trying to add to some maps the same collection of pairs with:

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val channelMap = mutableMapOf(
        "title" to setup.channelTitle,
        channelIdKey to setup.channelId)

    val userChannelsMap = mutableMapOf<String, Any>(
        channelIdKey to setup.channelId,
        "title" to setup.channelTitle)

    val messageMap = mutableMapOf(
        "text" to text,
        channelIdKey to setup.channelId,
        "updatedTimeStamp" to ServerValue.TIMESTAMP)

    val usersInfoMap = mapOf("videoOwnerName" to setup.ownerName,
        "videoOwnerId" to setup.ownerId,
        "requesterId" to setup.requesterId,
        "requesterName" to setup.requesterName)

    arrayOf(channelMap, userChannelsMap, messageMap).forEach { it.putAll(usersInfoMap) }

But I get:

MutableMap<String, Any> restricts the use of putAll(map)

is there any way to do it?

danielgomezrico

09/01/2016, 3:18 AM

why is that?

cypher121

09/01/2016, 3:42 AM

probably because of generic projections, but I'm not good with that stuff, so no idea what to do with it

cleiter

09/01/2016, 7:21 AM

@danielgomezrico i guess it's because the maps don't have the same generic types but `arrayOf`has to determine the common type, try to unroll the last line

bamdmux

09/01/2016, 7:59 AM

@danielgomezrico Or specify the types of the map, seeing the variable names I guess all are Map<String,Any>, right?

cleiter

09/01/2016, 8:37 AM

depends on the type of

channelIdKey

bamdmux

09/01/2016, 8:50 AM

in userChannelsMap he specifies the type and is String

danielgomezrico

09/01/2016, 2:52 PM

yeah all are

MutableMap<String, Any>

danielgomezrico

09/01/2016, 2:52 PM

I just wanted to reuse the userInfoMap

danielgomezrico

09/01/2016, 2:52 PM

or is there any other way?

danielgomezrico

09/01/2016, 2:52 PM

I had to specify there because there was a compilation error

jcomo

09/01/2016, 11:35 PM

I would go with the suggestion of unrolling the loop here. Its arguably more understandable and you don’t gain anything (at least from the context of the snippet) by having it dynamically done in a loop except for losing a couple lines

drfriendless

09/03/2016, 1:43 PM

usersInfoMap is not mutable, it's an immutable map. Use mutableMapOf to construct it.

oshai

09/17/2016, 8:07 PM

what do you think about this code that looks for companion object:

oshai

09/17/2016, 8:08 PM

@User uploaded a file: Untitled

Untitled.kt

oshai

09/17/2016, 8:08 PM

instead of using reflection

voddan

09/18/2016, 4:50 AM

does it work ?

voddan

09/18/2016, 4:56 AM

anyway, a

companion

may have any name, not just

$Companion

(which is the default)